The invention relates to a stent for treatment of stenoses.
Stenoses are innate or acquired vessel blockages or constrictions of tubular body tubes, such as, for example, windpipe, bronchial tubes, esophagus, bile ducts, urinary passages, aorta, and coronary or other body vessels. Stenoses are oftentimes caused by tumors which exert pressure upon the body tubes. Stenoses can be opened by surgical and non-surgical procedures. Non-surgical procedures involve stents which are introduced into the vessel in the area of the stenosis using catheter techniques. The stents assume the function as vascular prostheses for supporting the inner vessel walls.
Stents are available in different constructions and designs of the support frame. WO 96/26689, U.S. Pat. No. 5,861,027 A, DE 297 02 671 U1 or DE 295 21 206 U1 are mentioned here as examples.
The stents include a tubular support frame of metal which is made of several ring segments. The latter are formed by wave-like or meander-shaped struts which are sequentially joined in an endless manner via arcuate sections. Adjacent ring segments in longitudinal axis of the stent are linked by connectors.
Implantation involves compression of the stents, referred to in the art as crimping. When crimped, the stents are transferred with the aid of a suitable instrument into the area of the stenosis and deposited there, wherein the support frame is expandable from an initial state to a support state of comparably greater diameter. This expansion may occur spontaneously, when so-called self-expanding stents are involved, or may be realized with the aid of a suitable tool, a balloon catheter for example.
Practice has shown that the support frames oftentimes are either unable to provide the necessary radial forces to sufficiently resist a stenosis, or are so designed as to impede the function of the vessel. Other constructions, in turn, cannot be sufficiently crimped or are not flexible enough, when crimped, in order to be able to reliably follow the body vessels and its turns.